Corrosion-inhibitor packaging material



Nov. 7, 1961 J. M. LE BOLT ET A; 3,007,767

CORROSION-INHIBITOR PACKAGING MATERIAL Filed April 7, 1961 2Sheets-Sheet 1 INVENTORS.

Nov. 7, 1961 J. M. LE BOLT ET AL CORROSION-INHIBITOR PACKAGING MATERIAL2 Sheets-Sheet 2 Filed April 7, 1961 Hm mJUL/U m .rmuk

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fiDuOm NonOm Unite States 3,007,767 CORROSION-MGR PACKAGING MATEREALJohn M. Le Bolt, Deerfield, and Stanley W. Drigot,

Chicago, 111., assignors to The Cromwell Paper Company, a corporation ofIllinois Filed Apr. 7, 1961, Ser. No. 103,675 14 Claims. (Cl. 212.5)

This invention relates to improvements in chemicallytreated packagingmaterials for use in protecting metallic parts against rust andcorrosion. This application is a continuation-in-part of our co-pendingapplication Serial No. 21,276, filed April 11, 1960, now abandoned.

The use of packaging materials for the protection of metallic partsagainst rust and corrosion, for extended periods of time duringtransport, handling and storage, currently has acquired a wide practicein industry. Diverse chemical compounds variously applied to differenttypes of materials have achieved highly satisfactory results ineffectively inhibiting corrosion of such metallic parts. Preferredcorrosion-inhibitor compounds and methods of application to acceptablepackaging materials are disclosed in Patents Nos. 2,837,432, 2,829,945and 2,653,854. In general the practice is to impregnate and/ or coat thesurfaces of the packaging material with the desired inhibitor compound.

The main objects of this invention are to provide an improved pattern ofapplying the inhibitor compound to the packaging materials used forprotecting the metallic parts; and to provide improved packagingmaterials of this kind having a pattern of spaced-areas of the appliedinhibitor compound which achieves a greater eflicacy of corrosioninhibition than is currently attainable with other types ofcorrosion-inhibitor treated packaging materials.

In the accompanying drawings:

FIGURE 1 is a section of packaging material having an applied pattern ofcorrosion-inhibitor compound, comprising circular spots of the compound,such as was used in the hereinafter-explained efficacy tests;

FIG. 2 is a diagrammatic view of sections of packaging materialindicating comparative patterns of corrosioninhibitor applications;

FIG. 3 is a view of the type of test apparatus used to make the testverification;

FIG. 4 is a perspective view of one of the metal specimens used in thetests; and

FIGS. 5, 6 and 7 are diagrams showing the comparative results ofcorrosion inhibition obtained with the series of tests presently to bedescribed.

The essential concept of this invention involves the discovery thatpackaging material having a pattern of spaced-area applications ofcorrosion-inhibitor compound secures unexpectedly-superior results overpackaging material having the same amount of coated area but applied bythe usual over-all or continuous coating manner.

Packaging material embodying the foregoing concept comprises sheets 6one face of which has applied thereto spaced areas 7 of a preferredcorrosion-inhibitor compound.

Sheets 6, used for this purpose, may be any of the materials thatconventionally have been found to be acceptable for packaging metallicparts. More generally these are paper products, although on occasionother materials are used.

The packaging materials and inhibitor compounds described in thebefore-mentioned patents have insured wholly satisfactory results. Thecorrosion-inhibitor material, however, might be any of thecurrently-available compounds. The best results are believed obtainable3,007,767 Patented Nov. 7, 1961 with compounds of the nature set forthin Patents Nos. 2,829,945 and 2,837,432.

Obviously, there are various ways in which the desired pattern ofspaced-area application of corrosioninhibitor compound to the packagingmaterial may be made. A form of offset printing has been found quiteacceptable. The geometric character of the spaced treated areas isbelieved not to be critical. Either the treated or untreated areas couldbe of any desired shape. For example, as spots the areas may berectangular, triangular, or circular, all of which are included in thedescriptive term polka-dot hereinafter used. Or, the pattern might bespaced, long, narrow strips of the compound, or the compound may beapplied in the form of a signature or combination of letters of thealphabet, as in the case of a company name.

The spacing of the spots, strips or other design and the respectiveareas thereof is important in that the combined area of the treatedspots or designs on the surface of the packaging material, relative tothe total usable area thereof, must be sufiicient to provide thecorrosion inhibition required. Thus, the distribution of the spotsand/or designs should be substantially uniform and the distributionshould be such that any given portion of the treated material will havesubstantially the same proportion of treated to untreated area as anyother part of the material. 1

In the tests hereinafter described sheets of packaging material ofpredetermined dimension with 27.6% of the total surface area covered bythe spaced area application of corrosion-inhibiting compounddemonstrably proved better results in corrosion inhibition than a sheetof packaging material of one-third the size the entire area of which wascovered with corrosion-inhibiting com pound of the same density. Thisproved that the amount of inhibitor compound involved in the test wasnot a critical factor.

Similar results are also obtained with other ratios of treated area tototal sheet area and in this regard results commercially satisfactoryfor many purposes have been obtained with a ratio as low as 1 to 20, orwith the treated areas occupying approximately 5% of the total sheetarea. On the other hand and from the commercially practicalconsideration, tests show that the advantages of this invention rapidlydecrease in significance when the total of the treated area is greaterthan about 50 to 60 percent of the total area of the packaging materialsurface onto which the corrosion. inhibiting compound is applied, i.e.the efficacy of one compared to that of the other is so closely the sameas to make the change from the ordinary practice of coating the entiresurface of the packaging material commercially impractical.

The first mentioned relationship of test materials is diagrammaticallyindicated in FIG. 2. The two rectangles 8 and 9 at the left representsections of packaging material 6 of the same dimensional areas. Therectangle 10 represents a section of packaging materialfi approximatelyone-third of the area of the section 9. The section 8 is untreatedpaper. The: section 9 represents packaging material with a pattern ofuniformly spaced circular spots 7 of the corrosion-inhibitor compoundapplied thereto. The composite: area of these spots is approximately27.6% of the total area of section 9. Section 10 represents a standardproduction specimen of packaging material 6 the entire area of which hasthe inhibitor compound applied thereto in the manner heretoforecommercially used.

The hereinafter-described test (Table No. 1) which is merely arepresentative test, positively demonstrates that the polka-dot sample 9secured superior results over the full area treated sample 10.

The reason for this unexpected superior result is uncertain.Nevertheless it does occur. It isbelieved to be accounted for by aphenomenon similar'to that known as synergism-a reaction wherein theresult is greater than the sum of the parts. Stated in other words, itis a result that would seem to be logically unlikely from the factorsinvolved. Logically, for example, it would seem that a sheet area of apredetermined size, coated entirely with the inhibitor compound, wouldbe at least as effective as a sheet three times the size to which theinhibitor compound had been applied to spaced areas occupying a total ofnot more than one-third the sheet area. However, tests positively provedthe contrary.

Accessory advantages of the spaced-area pattern is the saving in theinhibitor compound required for protecting certain metallic parts; andthe fact that the pattern can be applied to the paper base or other websby means of a simple rubber roll impression plate.

It is quite possible that the fibrous structure of the untreated spacesbetween the treated areas provides channels for effecting a morebalanced vaporization of the inhibitor compound than is possible withthe entire area of a sheet of paper covered with the inhibitor compound.

Tests, which constituted a verification of this discovery, that aspaced-area pattern of the inhibitor compound would produce superiorresults over a full-area pattern, were carried out with devices asillustrated in FIG. 3 and in the manner presently to be explained. Thesetests, known as Accelerated Short Term Corrosion Tests, have been usedfor many years to evaluate the eiiectiveness of corrosion inhibitingpackaging materials.

These devices comprised quart jars 12, having a 3% mouth opening and 6/2 depth and equipped with Bakelite screw caps having an aluminum foilliner. A cup-like specimen holder 13, of Lucite 3 in diameter, having abottom wall 14 A" thick and vertical side walls extending above and ashort distance below the bottom wall 14, was provided to support thespecimens above the bottom of the jar in which a quantity of distilledwater was placed. The side wall of the holder extended below the bottomwall sufficient to space it above the water level and a plurality of Ainch holes 15 were formed in the holder bottom to allow free How ofwater vapor into the interior of the holder. A paper sample 16 was thenset into the holder against the inner side wall thereof, with the coatedsurface inward and the metal specimens 17 were set on the bottom of theholder so as to be partially surrounded by the paper sample. The holderwas then set into the jar for the test.

The metal specimens 17 were small cylindrical bodies, /8" diameter, ofSAE 1020 steel imbedded in Bakelite with one face of the body exposed.(See FIG. 4.) After being set into the Bakelite, these steel specimens17 were abraded, initially, with Black & Decker U-l412, 120 grit,open-grain sanding discs and later, at 90 to the first abrasion, withBehr-Manning Metallite cloth lightening sheets, 240 grit aluminum oxide.Such abrading was done to insure the surfaces being absolutely free ofrust or corrosion or other contamination. Immediately thereafter theseabraded specimens 17 were immersed in petroleum ether until ready forplacement in the test jar 12.

Three types of test were made in each of many series of tests, two withinhibitor-treated paper and one with untreated paper. The first of thetwo treated paper tests were made with a 2 /2" x 7 sample of paper,which is considered normal size for our test procedure, treated with aspaced-area pattern of inhibitor compound occupying 27.6% of the sheetarea. The second of these two tests was made with a %1" x 7" papersample the entire area of which was coated with the same inhibitorcompound. The third test in each series was made with a 2 /2 x 7untreated paper sample.

In tests #1 and #2, four jars were employed, three jars with twospecimens in each and one jar with a single specimen. In test #3 onlyone jar was used there being a single specimen in the jar for test. Inall cases all specimens were prepared in the same manner, and asdescribed above, and in all cases the specimens were prepared on thesame day that the comparative tests were run, all tests being runsimultaneously. In the case of each test, the specimens were subjectedto two full test cycles as explained below.

In preparation for the tests, the jars 12 after being thoroughly cleanedand rinsed with distilled water were supplied with 30 cc. of distilledwater. Then the paper samples were inserted into the specimen holders13, which had been cleaned in the same manner as the jars 12, so as torest against the inner surface of the holder wall, and the holders 13were placed in respective test ars.

Following this, and before putting the metal test specimen 17 into thejars, the jars were closed with covers having sheet aluminum liners andwere subjected to a preliminary equilibration period of 30 minutes at atemperature of F. This was to permit the respective jars 12 to fill withwater vapor and the vapor from the paper samples whereby the inhibitorvapors and the air both became in equilibrium with the ambientconditions in the jar.

The equilibration period having been completed, the jars were allowed tocool at room temperature for 45 minutes. Then the jars were opened andthe specimens 17 were placed on the holders in their respective jars 12which then were again sealed and stored for one hour at a 120 F.Subsequently, the jars were subjected to a 40 minute cooling periodunder ambient room temperature conditions after which they were placedin a 40 F. water bath for 15 minutes. The resulting water condensationon the specimens would produce corrosion unless protected by the vaporsfrom the inhibitor-treated paper samples. This constitutes one cycle ofthe test and then after visual examination of the specimens withoutremoving them from the jars, the test was repeated for a second cyclebut omitting the equilibration period.

The following is a tabulation of the results that were obtained withthese tests:

Table N 0. 1

Jar Number and type of paper Cycle I Results Cycle II Results OK OK SLPFSLPF OK PF OK SLPF OK F F F SLPF F SLPF F g F 30 BLANK F-Severe F-SevereExplanation of abbreviations: 30 is the basis weight of the paper. PD isa 27.6% polka-dot pattern. (9 in Fig. 2.) CONT means over-all orcontinuous coverage of the inhibitor compound on the paper sample of anarea approximately that of the samples used with the polka-dot tests (10in Fig. 2). BLANK refers to untreated paper. (8 in Fig. 2.) OK meansfree of rust except within Me of the outer periphery of the steelspecimen which is commonly regarded as acceptable. SLPF means slightpartial failure. PF means partial failure. F means failure, rustdistributed throughout face of specimen. F-Severe means practicallycontinuous rusting over entire face of specimen.

FIGS, 5, 6 and 7 are diagrammatic representations of the conditions ofthe respective specimens made immediately following the respective testcycle. The legends adjacent the respective circles conform with thoseused and explained in the foregoing tabulation. In the above paragraphswe have described in detail the procedure used in evaluating thisinvention.

For further evaluation of the hereindisclosed invention and todemonstrate the efiicacy of the spaced area Table No. 2

Percent Jar Number and type of paper age of Cycle I Cycle II normalResults Results width 30 CONT l 100 OK OK OK OK 30 GON T 2 50 F F F F 30CONT 3.- 30 F F F F 30 CONT 4 20 F F F F 30 CONT 5.--. 10 F F F F NOPAPER 6 F F F F In this test (Table No. 2) the sample of treated paperemployed in test jar #1 was a normal size test sample 7" long x 2 /2"wide and, as indicated, this sample gave full corrosion protection tothe metal test specimens. All of the other test jars produced definitefailure of corrosion protection. Test jar #2, however, which employed atest sample of over-all treated material of 50% of the normal width(i.e. 1%" wide), did not show as many corrosion areas or as advancedcorrosion areas as did the metal specimens in jars 3, 4 and 5, which hadbeen subjected to narrower samples of the over-all treated material, oras in the case of jar #6 which had no treated material.

Table No. 3, produced below, is representative of tests conducted todetermine the effectiveness of the spaced area treatment of packagingmaterial, according to the present invention, wherein the sum of thespaced treated areas is greatly reduced. In these tests normal sizesamples Were used, with the spaces between the treated areas such thatthe sum of the treated areas was only of the total area of the 7 x 2 /2"test strip and the test procedure employed was the same as aboveoutlined for the tests of Table No. 1, except that the tests wereterminated after one cycle.

As indicated by Table No. 3 the 5% spaced area treatment of thepackaging material is capable of giving better corrosion protection thanthat obtained with a 50% sample of over-all coated material, having 10times the total area of inhibitor compound application, as shown inTable No. 2. Although the tests represented by Table No. 3 wereterminated after only one test cycle, it is evident that packagingmaterial having a 5% spaced area application of the inhibitor compoundwill give substantial protection under many circumstances or conditionsof use.

From the foregoing it will be apparent that a new discovery has beenmade, in the already highly developed field of corrosion inhibitingpackaging materials, in that repeated tests show that a given total areaof inhibitor compound coating applied as an interrupted pattern affordsgreater protection than does the same total area of inhibitor compoundcoating applied as a continuous or overall pattern. In the light of pastexperience in the development and improvement of corrosion inhibitingwrapping materials this result does not follow the course of logic andis wholly unexpected. The reasons for the improved and unexpectedresults herein disclosed are at present unknown, or at least uncertain.However, it does appear that a synergistic-like effect is produced whichenhances the efficacy of the inhibitor material when it is employed inthe manner described.

It will be understood that the term packaging materials and wrappingmaterials as used herein are to be interpreted in their broadest senseand include metallic and non-metallic foils, textiles, and paper orpaper boards, as well as combinations of the same.

Although but one specific embodiment of our discovery has been hereinshown and described it will be understood that details of the manner ofpracticing the invention may be altered or omitted without departingfrom the spirit of the invention as defined by the following claims.

We claim:

1. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a packaging material having a pattern of spaced-areaapplications of a corrosion-inhibitor compound, the sum of the areas ofsaid spacedarea applications being sufiicient to prevent corrosion ofsaid metallic parts but not exceeding about fifty percent of the totalarea of said packaging material.

2. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a sheet material having a predetermined pattern ofspaced-area applications of a corrosion-inhibitor compound, the sum ofthe areas of said spaced-area applications being sufiicient to preventcorrosion of said metallic parts but not exceeding about fifty percentof the total area of said sheet material.

3. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a paper sheet having a predetermined pattern ofspaced-area applications of a corrosion-inhibitor compound, the sum ofthe areas of said spaced-area applications being suflicient to preventcorrosion of said metallic parts but not exceeding about fifty percentof the total area of said paper sheet.

4. A packaging material for inhibiting rust and corrosion of metallicparts, comprising a packaging material having a pattern of uniform-sizeuniformly-spaced area applications of a corrosion-inhibitor compound,the sum of the areas of said spaced-area applications being sufficientto prevent corrosion of said metallic parts but not exceeding aboutfifty percent of the total area of said packaging material.

5. A packaging material for inhibiting rust and corrosion of metallicparts, comprising sheeted material having a predetermined pattern ofuniform-size, uniformlyspaced area applications of a corrosion inhibitorcompound, the sum of the areas of said spaced-area applications beingsufficient to prevent corrosion of said metallic parts but not exceedingabout fifty percent of the total area of said sheeted material.

6. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a paper sheet having a predetermined pattern ofuniform-size, uniformly-spaced area applications of acorrosion-inhibitor compound, the sum of the areas of said spaced areaapplications being sufficient to prevent corrosion of said metallicparts but not exceeding about fifty percent of the total area of saidpaper sheet.

7. Means for inhibiting rust and corrosion of metallic parts, comprisinga paper sheet having a predetermined pattern of uniformly-spaced spotsof corrosion-inhibitor compound applied to the surface thereof adjacentsaid parts, the sum of the areas of said spots of corrosion-inhibitorcompound being sufficient to prevent corrosion of said metallic partsbut not exceeding about fifty percent of the total area of saidpackaging material.

8. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a packaging material having a pattern of spaced areaapplications of corrosioninhibitor compound, the sum of the areas ofsaid spacedarea applications of corrosion-inhibitor compound beingapproximately twenty-five percent of the total area of the surface ofsaid packaging material onto which said compound is applied.

9. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a sheet material having a predetermined pattern ofspaced-area applications of a corrosion-inhibitor compound, the sum ofthe areas of said spaced-area applications being approximatelytwentyfive percent of the total area of the surface of said sheetmaterial onto which said compound is applied.

10. Packaging material for inhibiting rust and corrosion of metallicparts, comprising a paper sheet having a predetermined pattern ofspaced-area applications of a corrosion-inhibitor compound, the sum ofthe areas of said spaced-area applications of corrosion inhibitorcompound being approximately twenty-five percent of the total area ofthe surface of said paper sheet onto which said compound is applied.

11. A packaging material for inhibiting rust and corrosion of enclosedmetallic parts, comprising a packaging material having a pattern ofuniform-size uniformlyspaced area application of a corrosion-inhibitorcompound, the area of the compound application being approximatelytwenty-five percent of the total area of the packaging material.

12. A packaging material for inhibiting rust and corrosion of enclosedmetallic parts, comprising sheeted material having a pattern ofuniform-size, uniformly-spaced area application of a corrosion-inhibitorcompound, the area of the compound application being approximatelytwenty five percent of the total area of the sheetedmaterial.

13. Packaging material for inhibiting rust and corrosion of enclosedmetallic parts, comprising a paper sheet having a pattern ofuniform-size, uniformly-spaced area application of a corrosion-inhibitorcompound, the area of the compound application being approximatelytwenty five percent of the total area of the paper sheet.

14. Means for inhibiting rust and corrosion of enclosed metallic parts,comprising a paper sheet having a pattern of uniformly-spaced spots ofcorrosion-inhibitor compound applied to the surface thereof adjacentsaid parts, the area of the compound application being approximatelytwenty five percent of the total area of the paper sheet.

References Cited in the file of this patent UNITED STATES PATENTS

1. PACKAGING MATERIAL FOR INHIBITING RUST AND CORROSION OF METALLICPARTS, COMPRISING A PACKAGING MATERIAL HAVING A PATTERN OF SPACED-AREAAPPLICATIONS OF A CORROSION-INHIBITOR COMPOUND, THE SUM OF THE AREAS OFSAID SPACEDAREA APPLICATIONS BEING SUFFICIENT TO PREVENT CORROSION OFSAID METALLIC PARTS BUT NOT EXCEEDING ABOUT FIFTY PERCENT OF THE TOTALAREA OF SAID PACKAGING MATERIAL.